Structural stability and evolution of terbium-doped silicon clusters and influence of 4f → 5d electronic transition mechanism on magnetism and appearance of photoelectron spectroscopy for TbSin0/- (n=6-18) clusters

The global minimal structures of terbium-doped Si clusters and their anions TbSin0/- (n = 6-18) are confirmed by employing the ABCluster unbiased global search technique combined with a B2PLYP double-hybrid density functional and comparing consistency of simulated and experimental photoelectron spectroscopy (PES). The results demonstrated that structural evolution patterns for neutral clusters prefer Tb-substitutional to Tb-encapsulated configuration starting from n = 16. While for the corresponding anionic clusters, the growth pattern adopts Tb-linked structures to encapsulated motif. The Natural Population Analysis revealed that the 4f electrons of Tb atom in TbSin0/- (n = 6-18) clusters participate in bonding. The way to participate in bonding is one 4f electron transition to 5d orbital ([Xe]6s(2)4f(9) -> [Xe]6s(2)4f(8)5d(1)), which significantly affects the cluster's magnetism and appearance of PES. The total magnetic moments of neutral TbSin and the corresponding anions maintain at 7 mu B and 6 mu B, respectively, which are larger than that of an isolated Tb atom. The HOMO-LUMO energy gap, relative stability, and chemical bonding analysis demonstrated that superatomic TbSi16- cluster is a magic cluster with fine thermodynamic and moderate chemical stability.